As is known, in mechanisms for imparting the typing action, the stroke of the type-carrying element against the paper is effected in a controlled way either positively through a cam driven by a transmission shaft, or by means of an elastic member, but always through a movement controlled by the motor.
In both the known cases, the intensity of the stroke depends on the rotation speed of the driving shaft of the motor so that, for instance, it can vary because of a sudden voltage rise, or because of friction in the associated mechanism causing a visible difference in the intensity of the print of the character on the paper, with serious consequences for the appearance of the typewritten product.
Furthermore in the known machines a mechanism is provided for the correction of the printing of the very small signs or characters, e.g. commas, dots, and so on, by reducing the intensity of the hammering.
Such mechanism picks up the signal from the key and transmits it, by means of rods or flexible-transmission or similar devices to the hammering device by an expensive connection train. There are difficulties with transmission of the signal and in discriminating the signal for the small letters from that of the capitals because the signal coming from the key is the same in both cases.